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Power source affects environmental impact of electric vehicles

An electric vehicle, like the Nissan Leaf, can pollute as much as a regular car, depending on where the power is generated. Photo Credit: Masahiko OHKUBO/Wikimedia Commons/CC-BY

Conventional thought is that “green vehicles,” such as hybrids and electric cars, are better to buy because they pollute less than traditional cars. However, where the electricity comes from matters a lot.

Facing the charges

A growing number of people are buying “green vehicles,” for a variety of reasons. Electric vehicles don’t use gasoline and are cheaper to operate. Both hybrids and electrics produce far less particle emissions than cars with internal combustion engines. Electric cars, in fact produce none.

However, in order to power an electric car, it has to be charged and generating electricity can be a dirty business. In fact, charging electric vehicles can produce more greenhouse and fine particle emissions than would be emitted by the same number of gas-powered vehicles, which is what a study of pollution in China just found, according to the Daily Mail.

Setting a coal

The study, which according to TG Daily was done by the University of Tennessee in Knoxville, looked at emissions data from 34 cities across China where citizens use electric and hybrid vehicles. The authors found that the amount of greenhouse gases and fine particles, produced by combustion of fossil fuels, was more than would have been emitted by the same number of gas-operated vehicles.

Though it may seem to defy logic, the reason is that China generates 85 percent of its electricity from fossil fuels. Coal accounts for 90 percent. Greenhouse gases and particles emitted by the power plants are in larger quantities than the accumulated gas and particle emissions from combustion engines.

Power source matters

Emissions produced by producing power to charge an EV depends on how the power is generated. For instance, according to British magazine Which?, producing the electricity to power a Nissan Leaf gives the car equivalent emissions of 106 grams of carbon dioxide per kilometer (about 170 per mile). The power industry in Britain emits an average 521 grams per kilowatt hour across all sources and 23 percent of its electricity was from coal power plants in 2010, according to The Guardian.

Power generation in the United States averaged about 1.341 pounds per kWh, or about 608.3 grams per kWh, in 1999, according to the Department of Energy. The Leaf goes about 3.16 miles per kWh of electricity, according to Consumer Reports, giving it emissions of 192.5 grams per mile for the United States average. However, emissions per kWh has dropped significantly since then. The United States derived 45 percent of its electricity from coal in 2010, according to the Energy Information Administration.

The base 2012 Ford Focus with an automatic transmission, according to FuelEconomy.gov, emits about 287 grams of carbon dioxide per mile. A Prius puts out 178 grams per mile, making the Prius “greener” than a Leaf to drive, using national averages. That said, a Leaf powered by zero-emissions power, such as from hydroelectric or wind turbines, has equivalent emissions of 0.